First article. When
specified (see 6.2), a sample shall be subjected to first article
inspection in accordance with 4.3.

3.2

Materials. The contractor shall select materials
capable of meeting all of the operational and environmental
requirements specified herein. The materials specified in
MIL-P-11268 are recommended, but are not mandatory.

3.2.1

Recycled, recovered, or environmentally
preferable materials. Recycled, recovered, or
environmentally preferable materials should be used to the
maximum extent possible provided that the material meets or
exceeds the operational and maintenance requirements, and
promotes economically advantageous life cycle
costs.

Weight. The total weight
of the biocular eyepiece shall not exceed 10 pounds.

3.5

Performance
characteristics.

3.5.1

Field of view to the eye. The field
of view to the eye shall be not less than 39
degrees.

3.5.2

Magnification. The
on-axis magnification shall be not less than 4.5
times.

3.5.3

Field overlap. The
biocular eyepiece shall provide at least 50 percent field
overlap with field overlap calculated using the diameter and
not the area of the overlapping images. These conditions
shall be satisfied at the fixed diopter setting.

Field flatness.
The biocular eyepiece shall have a flat tangential
field within plus or minus 1/2 diopter across the outer 50
percent of the 40-mm format and within plus or minus 1/4
diopter across the central 50 percent of the 40-mm format at
the fixed diopter setting.

3.5.6

Resolution. The
visual axial resolution (central 25 percent of the field of
view) of the biocular eyepiece shall be not less than 35.9
line pairs per millimeter. The remaining field of view
shall resolve 17.9 line pairs per millimeter.

3.5.7

Transmission. The
transmission of the biocular eyepiece shall be at least 85
percent over the entire aperture for the region of spectral
output of a P-20 phosphor.

Linear distortion. T he
linear distortion of the biocular eyepiece measured at the
fixed diopter setting shall be 5.3 plus or minus 1 percent
barrel distortion at the edge of the 40-mm format.

3.5.10

Back focal distance.
The back focal distance shall not exceed 0.10 inch for
an object projected 400 mm behind (towards the biocular) for
the nominal 60-mm exit pupil.

3.6

Environmental conditions.

3.6.1

Temperature shock. The biocular
eyepiece shall operate after exposure to sudden changes (5
minutes or less) in the thermal environment from 21oC to
-32oC and from 21oC to 52oC. No chemical deterioration
shall result from this exposure.

3.6.2

Shock and vibration. The biocular eyepiece
shall meet specified performance after being subjected to
shock and vibration levels in Table I.